Here's what Bungie said about the lack of matchmaking for raid-like missions in Destiny

The lack of matchmaking in Destiny for endgame dungeons struck a nerve with some people. On the one hand, the ability to only play these missions with people you know is nice. On the other, the fact that you can't just randomly hop on one night and complete them is a bit disappointing.

Here's what Bungie, specificially writer Luke Smith, said on the matter:

I understand everyone's frustration about the decision to not have matchmaking in a post-matchmaking world. I also understand the limitations that this places on the activity's adoption at scale.

That barrier to entry - the requirement that you get a group of people together and venture into something that is going to challenge your ability to work together (first) and your thumbs (second) - is a barrier I was willing to erect to preserve the activity goals.

Bleeding edge hardcore groups will invest some significant amount of time in figuring out the encounters and making their way through the Vault.

I fully expect groups to beat Normal mode in the first week its available.

· This is intentional, I'd like any group that is motivated and willing to cooperate to make their way through the Raid on Normal. I've talked some about thumbskill challenge vs. investment challenge vs. cooperation challenge in some interviews, and the Normal Raid difficulty prioritizes cooperation challenge and investment challenge.

I expect Hard mode to take longer.
Once your group learns the encounters, you will be able to get through the Raid significantly faster than 3 hours.

However, the first time through, learning everything and arranging your group will take some hard-to-predict amount of time until some clan releases their strategies on YouTube.

The Vault of Glass is in many ways an activity that will build groups from the disparate people who come together to try and make their way through it. It's very much a team-building exercise.